Nothing in the universe is static. In the Milky Way, billions of stars orbit the galactic centre. Some stars such as the Sun are quite consistent. The Milky Way is like a dance but it isn’t a group of professionals but it’s more like a group of unprofessional people who are desperately trying to kick each other. This makes the galaxy dangerous. Our solar neighbourhood is constantly changing with stars moving hundreds of kilometres every second. Only the vast distances between the angry people (objects) protects us from the dangers out there. Thinking about it, we could get unlucky in the future. We don’t really know but if some object takes the wrong decision to hit us, then… we can’t really do anything except prepare for it. We could also be subjected to a gamma-ray burst or a supernova which is a huge cause of concern if we detect it. What if we just move the entire solar system out of the way?
To move the entire solar system right out of the way, we need to use a stellar engine. A stellar engine is a megastructure that can move a star through the galaxy. It’s the type of thing that could be built by a Dyson swarm level civilisation. When we become that, we will probably think about ourselves in millions of years. As we always do, we probably will try our hardest to live for as long as possible and if a huge asteroid, gamma-ray burst, supernova has taken the wrong decision to hit us; we will have to use a stellar engine to literally shoot ourselves out of the way of that. How do we make a stellar engine? There are many designs for the Stellar Engine but I picked 2 designs that make sense with the physics that we have today.
Shkadov thruster
The Shkadov thruster works on the same principle as a rocket. You shoot something in one direction to go in the other direction. In this case, instead of rocket fuel, we use photons from the sun. The photons release momentum. The Shkadov thruster reflects up to half of the solar radiation of the Sun to slowly move it. The picture above is a bit misleading though because the Shkadov thruster can’t be placed like that or else we could burn the Earth with too much Sunlight or freeze the Earth with low sunlight, thus the only safe place to put a Shkadov thruster is on the poles of the Sun. This means that we can only move the Sun vertically in the plane of the Solar System. For a civilisation that can build a Dyson swarm and Skyhook, a Shkadov thruster is not something too hard.
The Caplan Thruster
The Caplan Thruster was invented by Matthew Caplan of Illinois State University. It works quite a lot like a traditional rocket. It’s a large platform powered by a Dyson sphere that gathers matter from the Sun to power nuclear fusion. It shoots out a very fast jet of particles at nearly 1% the speed of light out of the solar system. The other jet is to prevent the megastructure to catapult itself into the Sun; it does that by pushing the Sun, like the trains which have a locomotive pushing the train from behind but in this case, it is pushing from the front. The Caplan thruster requires a lot of fuel, millions of tons per second. To gather this fuel, the Caplan uses very large electromagnetic fields to funnel hydrogen and helium from the solar wind into the engine. The solar wind doesn’t provide fuel and that’s why we need the Dyson swarm. Using the Dyson Swarm we can focus the light of the Sun on to the Sun. This heats up small regions of the Sun which lifts billions of tons of mass off the Sun. This mass has to be separated into Hydrogen and Helium. Helium is burned explosively in thermonuclear fusion reactors. A jet of radioactive oxygen at a temperature of nearly 1 billion degrees Celsius is expelled and becomes our primary source of propulsion. As I wrote a few lines ago; to prevent the engine to crash into the Sun, we do this by accelerating the collected Hydrogen with electromagnetic fields using particle accelerators and shoot a jet back at the Sun. By doing this, we can balance the thruster and transfer the thrust of our engine back to the Sun. The Caplan Thruster can move the Sun by 50 light-years in just 1 million years. 1 million years is certainly an unthinkable amount of time but it is enough to dodge a supernova. With such a megastructure, we will be able to turn our entire Solar System into our own Space ship. It may even be possible to escape the galaxy entirely and expand beyond the Milky Way. Stellar engines are the kind of machines built by civilizations thinking not in terms of years or decades but aeons. Since we know that our Sun will die one day, a stellar engine could allow the far future descendants of humans to travel to other stars without ever having to venture into the terrifying dark abyss of interstellar space. Till we make a stellar engine, we are subjected to the universe and the decisions it will take. The descendants of Humans may want to set sail to explore the universe while being on their home planet. The future is uncertain so we can’t say we won’t have to build a stellar engine, when we detect something that will cause concern for us, we could have to create something like this. We could know in advance but as I said in my “Will We Go Extinct” post, Damocloids could come as a surprise. Anyways, small Damocloids can’t wipe out humanity. The Universe is very much dangerous and I think that we may have to build something like the Caplan thruster. If we do have to build a Caplan Thruster, it would spark the start of an interstellar civilisation. I have a post that is coming soon so until then, bye!
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